Usually, micro-lens arrays are used in net-like distributed light guide plates for equably guiding light. The micro-lens array has a plurality of hemispherical lenses. The micro-lens array is ususally made of a transparent material such as polycarbonate or polymethyl methacrylate (PMMA) by heat press molding. Before molding the micro-lens array, a mold core having a plurality of tiny grooves is made using electroforming micro molding lithography. A transparent base is then pressed by the mold core under high temperature and high pressure in a manner so as to create a net-like micro-lens array. The hemispherical lenses are formed by the cohesion and surface tension of the base material under high temperature and high pressure. Thus, the hemispherical lenses may not have the same shape as the tiny grooves of the mold core. Therefore, the micro-lens array thus manufactured may be imprecisely molded.
FIG. 1 shows a typical process for making the micro-lens array. A base 10 is softened under a temperature higher than its glass transition temperature. The base 10 is then pressed under high temperature and high pressure by a mold core 20 which has a plurality of tiny grooves 22 thereon. The base 10 is distorted to fill the tiny grooves 22 under the pressure of the mold core 20, thus forming a plurality of hemispherical micro-lenses 12. During the process of making the micro-lens array, it is very important to control the temperature of heat pressing mold.
A typical method for controlling temperature is to use a water circulation cooling system. However, the water circulation cooling system is slow to reach a predetermined temperature when the molding temperature changes. Furthermore, the water circulation cooling system can take up a lot of space.
Therefore, it is desirable to obtain a temperature control apparatus which can overcome the above-described problems.